Silver nanowires were formed into random networks by using spin coating and spray deposition techniques. As a first step, electro-optical properties were optimized using an optimal nanowire density. The latter also depended on the nanowire morphology. As a second step, ex-situ annealing experiments combined with (in-situ) SEM experiments and TEM imaging were performed to gain more insight into thermal instabilities and associated defects. Annealing under atmosphere at 280°C was performed and for a given nanowire density, a resistance minimum at a certain temperature was systematically observed. The decrease in electrical resistance was attributed to both desorption of organic residues and above all, local sintering at the intersections between nanowires as observed by SEM imaging. Higher temperature caused morphological instabilities (known as “Rayleigh instabilities”) resulting in a sharp loss of electrical conductivity. Optical measurements did not show large variation of transmittance up to the onset of these Rayleigh instabilities. Finally, embedding of the nanowires in ZnO was demonstrated. We show that embedded nanowire networks are thermally stable well above 300°C while electro-optical properties are only slightly degraded. ZnO nanoparticles are assessed as potential candidates too for such an endeavor.